The Paleogene is a geological period that lasted from about 66 to 23 million years ago. It follows the Cretaceous period and is part of the larger Cenozoic Era. This period is significant for the rapid evolution and diversification of mammals and birds after the mass extinction event that wiped out the dinosaurs. During the Paleogene, the Earth's climate was generally warm, leading to the development of lush forests and diverse ecosystems. The period is divided into three epochs: Paleocene, Eocene, and Oligocene, each marked by distinct changes in flora and fauna, as well as shifts in global temperatures and sea levels.